Belonuchus trochanterinus ( Sharp, 1885 )

Márquez, Juan & Asiain, Julieta, 2022, Taxonomy of the Mexican species of Belonuchus Nordmann (Coleoptera: Staphylinidae), Zootaxa 5152 (1), pp. 1-129 : 48-49

Belonuchus trochanterinus ( Sharp, 1885)

Figs. 4c , 13a , 14g , 16i , 19b , 22h , 28a

Philonthus trochanterinus Sharp, 1885: 417 . Belonuchus trochanterinus comb. nov. ex Philonthus ( Navarrete-Heredia et al. 2002) .

Total body length 11.1 mm (range 10.5–12.1 mm). Black on head, antennae, pronotum, scutellum, fifth visible abdominal segment (except anterior border), sixth visible segment and abdominal styli. Reddish on elytra, sterna (except posterior half of prosternum which is black), legs, visible abdominal segments 1–4 and anterior border of fifth. Brown in mandibles, maxillary and labial palpi and genital segment.

Head: transverse (ratio 0.76, range 0.68–0.82). Dorsal surface with sulcate longitudinal midline visible only in anterior half of head; front weakly foveate near anterior margin. Eyes slightly more than 0.5 times the cephalic lateral length, not protruding laterally. Antennomeres 4–6 elongate, 7–10 as long as wide. Mandibles longer than head (ratio 1.25, range 1.08–1.57); each with two well separated teeth (basal and middle), mandibular channel moderately developed, external margin widely separated from internal margin at their base, internal margin carinate, extending beyond level of middle tooth. Apical palpomere of maxillary palpi slightly longer than preapical palpomere; apical palpomere of labial palpi nearly 1.25 times longer than preapical palpomere. Head wider than pronotum (ratio 1.16, range 1.13–1.20). Neck in ventral view with microsculpture a little coarser than on ventral surface of head.

Thorax: pronotum with five punctures in left and six punctures in right dorsal row, or five punctures in each row; pronotum slightly longer than wide (ratio 1.11, range 1.05–1.15) and almost as wide at anterior corners than at posterior corners (ratio 1.02, range 1.00–1.06). Scutellum with punctures denser than on elytra, latter with sparse punctation, with pale, fine setae. Anterior half of prosternum reddish and posterior half black, weakly elevated before anterior margin. Intercoxal process of mesoventrite shield-shaped; transverse discal ridge broadly U-shaped, not meeting margin of intercoxal process laterally. Profemur with external row of spines initiating near basal third and not reaching apex, spines small, shorter than spines placed near apex of internal margin. Metatrochanter modified like a hook that is moderately longer and distinctly curved and acute at apex, at most 1/3 as long as length of metafemur ( Fig. 13a ); metafemur moderately curved at level of overlap with hook; metatibia clearly curved in apical third. Tarsomeres flattened dorsally.

Abdomen: first visible tergite with posterior basal transverse carina straight and well developed; visible tergites 2–3 with posterior basal transverse carina not completely developed, visible at center and becoming irregular toward sides until it fades; adjacent depressed area rather shallow and with wide-superficial punctures denser than on remainder of tergites, where punctures being fine and moderately dense, with short and long combined setae. Sternites with wide-superficial punctures notably denser than on tergites, combined with fine punctures. Male pregenital sternite with distinct emargination at posterior margin ( Fig. 16i ). Male genital sternite moderately elongate (2.75 times longer than wide), slightly asymmetrical, anterior portion occupying 42% and posterior portion 58% of its length; apical emargination deep ( Fig. 19b ). Abdominal styli very wide and flattened at apex, wider than width of metatibia, ventrally with very dense dark setae ( Fig. 14g ).

Aedeagus: length 1.8 mm; cone-shaped, apex moderately acute; sides becoming regularly wider toward base; basal half notably wider than apical half; internal sac visible ( Fig. 22h ).

Variability. In addition to the variation indicated in the measurements and ratios of the description, and in the number of punctures in dorsal rows of pronotum, the mandibular channel is better developed in the largest specimen, the prosternum may be almost black, anterior femur of males with the row of spines developed over almost the entire length of the external margin, with a space before the apicalmost spines as if one or two of them were missing, the male metatrochanter modified like a hook may be as long as 0.33 to 0.50 times the length of the metafemur, and the metafemur may vary in curvature at the level of overlap with the hook.

Taxonomic comments. As indicated in the taxonomic comments of B. tenuistylus , both species have been confused in the past because they are somewhat similar, although they can be separated by means of the widened abdominal styli in males of B. trochanterinus . The recent review of two male specimens from Los Chimalapas, Oaxaca, have allowed the first correct record of B. trochanterinus in Mexico. In taxonomic comments of other species with which B. trochanterinus can be confused, characters that help distinguish them have been included.

The redescription of this species is based on three male specimens that do not belong to the type series but were compared with it. The type specimens were studied at the beginning of the study (more than five years ago), when there was uncertainty about including descriptions and specific characters. The types were returned to the NHM, and at the time of preparing the descriptions with comparable information for each species, they were no longer available. Lectotype of this species is designated here by taking into account Article 74.7 of the ICZN and its recommendations for establishing as accurately as possible the correct identity of this species.

Type material examined (four males, three females): Lectotype (male, NHM): “ Philonthus trochanterinus Type D. S. Capetillo, Guat. Champion (on the plaque with the specimen) / Sp. figured / B.C.A. Col. I. 2. Philonthus trochanterinus Sharp / Syntype / Lectotype Philonthus trochanterinus Sharp, 1885 ; Márquez & Asiain des. 2022” . Paralectotypes: “ Philonthus trochanterinus Type D. S. Capetillo, Guat. Champion (on the plaque with the specimen) / B.C.A. Col. I. 2. Philonthus trochanterinus Sharp / Syntype ” (m 2, f 1, NHM). “Capetillo, Guatemala, Champion / B.C.A. Col. I. 2. Philonthus trochanterinus Sharp / Syntype ” (f 2, NHM). “ P. trochanterinus D. S. Capetillo (in the plaque with the specimen) / Capetillo, Guatemala, Champion / B.C.A. Col. I. 2. Philonthus trochanterinus Sharp / Syntype ” (m 1, NHM) . Additional material examined (three males): Mexico : Oaxaca: “ San Miguel Chimalapa, San Antonio, El Retén, El Gringo , N16.6836°, W94.2623°, 1600 m, NTP-80, VI-VII-2013, E. Mora y L. Delgado cols.” (m 1, IEXA) . Same data, except “ N16.6787°, W94.2629°, bosque mesófilo, coprotrampa, 22-VII- 2017, E. Mora col.” (m 1, IEXA) . Guatemala: Jutiapa: “ Jerez, Volcán Chingo , N14.11522°, W89.73026°, 1610 m, bosque de encino-nuboso, en hojarasca cernida, 24-VIII-2014, M. Barrios col.” (m 1, CC-UAEH) .

Figures

FIGURE 4. Dorsal view of males of: a) Belonuchus tenuistylus (holotype), b) B. tepoztecus (paratype), c) B. trochanterinus, d) B. zunilensis (lectotype), e) B. bidens (syntype, NHM©), f) B. bidens, g) B. erichsoni, h) B. jalappensis. Scale bars = 2.5 mm.

FIGURE 13. Ventral view of the left posterior leg of males of: a) B. trochanterinus, b) B. tenuistylus, c) B. zunilensis, d) B. rufipennis, e) B. mixtecus, f) B. pollens, g) B. ephippiatus, h) B. aenigmaticus, i) B. iridescens, j) B. viridipennis. Tarsomeres of posterior leg of males of: k) B. colon, l) B. ephippiatus. Yellow ovals: median longitudinal groove.

FIGURE 14. Dorsal (left) and ventral (right) view of the first four visible abdominal segments of males of: a) Belonuchus singularis, b) B. tepoztecus. Abdominal styli of male of: c) B. alternans, d) B. confusus, e) B. singularis, f) B. magnistylus (right: detail of left stylus in ventral view), g) B. trochanterinus (right: detail of left stylus in ventral view).

FIGURE 16. Male pregenital sternite of: a) Belonuchus moroni, b) B. dichrous, c) B. flavipennis, d) B. aenigmaticus, e) B. nigerrimus, f) B. juanmorronei, g) B. godmani, h) B. magnistylus, i) B. trochanterinus, j) B. rufipennis, k) B. basiventris, l) B. connexus, m) B. xanthomelas, n) B. ephippiatus, o) B. optatus.

FIGURE 19. Male genital sternite of: a) Belonuchus tepoztecus, b) B. trochanterinus, c) B. zunilensis, d) B. bidens, e) B. erichsoni, f) B. jalappensis, g) B. mixtecus, h) B. pollens, i) B. rufipennis, j) B. basiventris, k) B. connexus, l) B. longitarsus, m) B. rufiventris, n) B. xanthomelas, o) B. ephippiatus, p) B. moroni. Scale bars = 0.5 mm.

FIGURE 22. Ventral (left) and lateral (right) view of the aedeagus of: a) Belonuchus oxyporimimus, b) B. oxyporinus, c) B. pulcher, d) B. rufisternus, e) B. singularis, f) B. tenuistylus, g) B. tepoztecus (at center detail of the paramere), h) B. trochanterinus, i) B. zunilensis. Scale bar = 0.5 mm (all figures).

FIGURE 28. Geographical distribution in Mexico and Guatemala of: a) Belonuchus colon, B. tenuistylus and B. trochanterinus; b) B. oxyporimimus, B. pulcher and B. juanmorronei.